This invention relates to apparatus for collection of blood as a therapeutic agent, and more specifically to such apparatus featuring provisions for collection of prescribed amounts of blood from individual donors with little or no human assistance. The apparatus in accordance with the invention lends itself to use at blood banks, hospitals, blood donation cars, and any other institutions or agencies where blood is donated for transfusion and other purposes.
Efficient collection of blood from as many donors as possible is a key factor for the extensive practice of transfusions and related methods of therapy at numerous medical organizations existing today. The usual practice for blood collection involves the use of a disposable bag, fabricated from polyvinyl chloride in sheet form, for each single donor. The bag has a pipe of pliant material extending therefrom and terminating in an intravenous needle. An adequate amount of anticoagulant is previously introduced into the bag in order to prevent the clotting of the collected blood.
In the use of the collection bag the needle is thrusted into a vessel of the donor, with the result that the blood flows through the pipe into the bag by virtue of the blood pressure of the donor himself. Before the collection the donor can choose the amount of blood he will donate at one time from between 200 cubic centimeters (cc) and 400 cc, although, of course, these values may vary from country to country. A collection bag having a capacity matching each donor's choice is used for collection. In the applicant's country, law permits collection errors up to+10 percent of the amount chosen by the donor, there being no regulation against shortages.
Thus, for the collection of the required amount of blood within the tolerance limit, a supervisor has usually had to attend to each donor throughout the course of donation. This has necessitated an expenditure of substantial energy. For it takes five to ten minutes, depending upon the donor's blood pressure and vessel size, to collect a preselected amount of blood from one donor by the above conventional method.
A more advanced collection system is found in Japanese Patent Publication (KOKOKU) No. 51-3153 published Jan. 31, 1976. This known system teaches the use of a hermetically enclosed space in which an inflatable collection bag is placed. As a partial vacuum is created in the enclosed space, a prescribed amount of blood is drawn from the donor's body into the bag more quickly than if the blood is fed solely by the blood pressure of the donor. This advantage is offset, however, by the difficulties arising for system makeready when different amounts of blood must be collected from successive donors. An additional weakness is that the amount of blood that has been collected is not readily apparent to the supervisor during the progress of donation.
It has also been suggested to measure the amount of collection by weight, rather than by capacity, as disclosed in Japanese Utility Model Publication (KOKOKU) No. 58-54090 dated Dec. 9, 1983. Being based on the principle of the spring balance, the apparatus according to this utility model is unsatisfactory in the accuracy with which the collected blood is weighed. The accuracy of weighing becomes even worse when, as is standard in the art, the bag is shaken during collection for the intimate intermingling of the collected blood and the anticoagulant.
The shaking of the bag requires the oscillation, rather than rectilinear reciprocation, of the platform on which the bag is mounted during collection. The accurate weighing of the collected blood on the pivoted oscillatory platform demands additional considerations that must go into the design of the apparatus.